Why did we evolve the ability to laugh? Crying is a way of showing pain, amongst other things. But what purpose did laughing server to early man?
It’s what separates us from the animals, except the hyena.
Seriously, it’s probably an evolutionary advantage as it relieves stress.
Weaseling out of things is what separates us from the animals, except the weasel.
H. Simpson
I hate to rain on anybody’s parade; but it’s possible to look too hard for evolutionary explanations for human characteristics.
I have serious doubts about the contribution of a laughter response to increased survival and reproduction through natural selection. Sexual selection, maybe… I guess humorless people don’t have much success with the opposite sex, but that’s in a very modern context and may not be representative of human development over evolutionary time scales. Anyone have a good explanation of how this might work?
Ernie Kovacs would suddenly blurt out “Why are you laughing?”
He was serious. Why was it funny? Why did you find it funny? Why did large groups find it funny?
For that matter, why did kings have jesters?
Our pets seem to have the ability to show pain and depression on loss of an owner. They also seem to have the
ability to show pleasure.
We’re going to need some of our bioligists to give us the latest on laughter=endorphins.
Desmond Morris provides the best (actually the only) explanation I have heard about laughing. He points out that babies are born with crying ability. This action (in babies and adults) consists of watering eyes, opening the mouth, pulling back the lips, exagerated breathing, intense expiration with high pitched vocalizations.
The moods are different but the responses are very similar to when we laugh. The big difference is that the long wail becomes segmented, smoother and lower in tone.
Crying occurs immediately after birth but laughing does not occur until the 3rd of 4th month, about the same time as parental recognition. Morris states that as a result of becoming imprinted on the mother, the baby becomes open to mixed signals. If the mother startles the baby, she is no longer just a fear stimulus (like she was earlier or as other adults are). She can give a double signal “There may appear to be danger but because it is coming from me, you do not need to take it seriously.”
The response is half a cry and half a parental recognition gurgle. The laugh says “I recognize that a danger is not real”. Notice that the things that cause an infant to laugh are shock stimuli: peek-a-boo, hand clapping, bouncing on a knee, and lifting high. But they are done by a protector.
The response becomes fully developed as we get older or at least it did a long time ago in our evolutionary history.
This actually sounds similar to what comedians have tried to define as one type of “joke”: a set-up with an unexpected outcome.
So you’re saying a laugh is a cry with an interruption of surprise.
I dunno. That almost sort of explains it, except it’s very unsatisfactory to me.
Most of the explanations I’ve heard point to laughter as a defense mechanism. It’s an automatic reaction to a perceived threat. If you look at the higher primates (as well as lower primates and other animals, I suppose), when they are threatened, their lips pull back to expose their teeth, and they make guttural “coughing” noises.
Desmond Morris and others have pointed to this as a possible evolutionary predecessor to laughter.
In a different thread, Dopers were trading jokes that we shouldn’t laugh at, but still do. It’s similar to Schadenfreude (sp?), which is the act or trait of laughing at the misfortune of others. Dennis Miller did a show on that subject once, and it was a wonderful commentary on humour.
So–why do we laugh at things that are offensive or harmful to others? The explanation that I believe and prefer (though if I find out that it’s not true, I’m over it) is that offensive and harmful things threaten us and, as mipsman pointed out, once we realise that the threat is not real, or the danger has passed (similar to the maniacal laughter after riding a roller coaster), our primal reaction is to bare our teeth and “bark.”
I don’t know about you, but I laugh at stuff that’s funny. 
I think the ideas about laughter as co-opting a pre-existing signal or response for a expressing mirth have some merit.
After all, even if laughter is a cry of recognition or similar to a bark, there’s no particular reason laughing, as opposed to some other signal, would confer a selective advantage, so it would be easier to co-opt something already in the animal’s repertoire for communicate glee.
How much evidence is there to back up this idea? Laughter is similar to crying and barking, but is that because they’re all manners of expression adopted with the same constraints (like vocal range) or because one is derived from the other?